• Baseline Protocol: the original protocol introduced in version 1.0 of the Qi Power Class 0 specification,
which uses Power Receiver to Power Transmitter communications only.
• Extended Protocol: added in version 1.2 of the Qi Power Class 0 Specification to support bidirectional
communications and enhanced foreign object detection (FOD) features. Version 1.3 of the Qi Specification
adds data transport stream functionality and authentication options.
• Selection: This is the default device state. The analog ping and Q-factor measurement are performed here
to lower the power consumption of the device when Rx is not present and to prevent current consumption
spikes in case of digital ping being transmitted into a foreign object.
• Digital ping: this phase is an interrogation session during which is the potential power receiver expected to
reply through amplitude shift-keying (ASK) modulation as defined by the Qi specification. After a valid
power receiver is detected, the transmitter proceeds to the Identification & Configuration phase.
• Identification & Configuration: this phase is aiming to identify the receiver and to gather information
necessary for a stable and reliable power transfer, such as the maximum power or FSK communication
parameters, baseline/extended protocol capability. After receiving the information, the power transmitter
creates a power transfer contract, basically a summary of the operational parameters. After the power
receiver is identified, the power transmitter proceeds to the power transfer itself (in case BPP is used).
If both the Rx and the Tx support Extended power profile, the devices proceed to Negotiation phase before
entering power transfer.
• Negotiation: this phase is used only in EPP. During this phase, the devices communicate additional
parameters of the power transfer, such as the reference power, FOD parameters etc. This distinct EPP
from BPP - the Tx also communicates to the Rx (as opposed to BPP, where communication only flows from
the Rx to the Tx).
Before the power transfer phase, the calibration phase is performed for FOD calibration in various load
conditions.
• Power transfer (also EPP power transfer): this is the final step. The power transmitter initially increases and
subsequently modulates the transmitted power in response to control (feedback) data from the receiver.
The receiver periodically sends information to the power transmitter, such as required power (CEP),
received power (RPP) etc., which are used to maintain a closed control loop. If a critical event (e.g.,
overvoltage, overcurrent or overtemperature) occurs, the power transmitter shall terminate the power
transfer immediately.
UM3286
Device description and operation
UM3286 - Rev 1
page 13/84
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